X-ray installations, in particular medical imaging X-ray equipment such as computer tomography X-ray equipment, for example, have one or a plurality of X-ray emitters, whose rotatably mounted rotary anodes for generating X-ray radiation can be exposed to optionally focused electron beams. The region, in which the electron beam impinges on the material of the rotary anode, is usually referred to as the focal spot. With X-ray emitters, the anodes of which are designed as rotary anodes, normally these anodes are typically set into rotation via an electric drive, in order to distribute the heat emerging in the focal spot over a larger region of the rotary anode.
It has transpired that the position and the extent of the focal spot can vary when the X-ray emitter is operated. This causes fluctuations in the X-ray radiation that is generated, which can have a negative effect on the quality of the X-ray images acquired.
To counteract this, DE 103 01 071 A1 proposes carrying out a determination of the position of the focal spot and regulating the position of the focal spot in the traditional way as a control variable, that is, a value for the variable control parameters required for adjusting the control variable is generated using a control deviation of a measured actual value for the control variable from a given set value. The disadvantage with such a procedure is that measurable deviations in the control variable—in this case, that is, the focal spot position—first have to be available for a compensation to be able to ensue.
Due to the control dynamics, a movement of the focal spot which depends on the amplitude of the original, that is, not on the compensated focal spot movement, is not included. Moreover, with a direct, active control, it is necessary to determine the spatial position and extent of the focal spot, which involves a plurality of sensors. Nevertheless, such methods that are implemented in the form of control circuits are designed to detect and, where necessary compensate for, disruptions of both known and unknown origin by determining the focal spot position.